355 Build

[dz1087]

Looking to liven up my 355. Had it rebuilt 8,000 miles ago to stock specs. Looking to get a bump in hrsprs and torque. My initial build thoughts below:

Not changing out bottom end, so this stuff stays:
4.020" bore
stock rods
stock crank
7cc dish pistons @ .025 deck clearance

Stuff I'm looking to change:
Aluminum dual plane intake manifold
Aluminum 180cc (64cc chamber) heads
Lunati 268 Voodoo flat tappet
2400 stall 700r4

Ram horn exhaust manifolds are probably going to stay as I don't want to fool around with exhaust work and leaky headers. Rear is already a 3.42 limited slip. Running a Q-Jet 4MV for fuel with stock mechanical fuel pump.



As mentioned drivetrain is currently sitting at stock specs with a TH350c and 3.42 Posi rear end. Understanding that the cam I have listed likes to have a 2400 stall speed, I'm fine with getting that for the TH350, but I think I would rather go ahead and grab a 700R4 with the 2400 stall.

Thoughts?

[68post]

Yes, if you use heads with pretty decent exhaust flow you won't need a dual pattern cam - altho the cast iron manifolds will hurt performance, especially torque production over the complete range.
Single pattern cams help your output below 4,000/4,500 rpm.

The VooDoo cams are great and created (originally) by a master Mr. Harold Brookshire, but you are in the duration range I'm considering for a 407ci engine with 10.5 comp with a manual trans and may be a bit too high for your combined: proposed stall range, weight, gearing, and compression. The lower first gear of a 700R4/4L60 will help with negating some of these effects.

Performer EPS intake would be my first choice, and your Qjet is perfect.

AFR Eliminator heads are at the very top of the aluminum heads, (you only need the 180cc version), next brand of heads are Profiler - which can actually make more HP than AFR if they're ported (AFR Eliminator heads only come as CNC ported).
And I would prefer 58cc chambers with your low compression setup, but be aware your quench is terrible with anything larger than a very thin shim type head gasket.

There are iron head choices also and they will work with shim gaskets perhaps better than AL. You can have heads flat and/or angle milled to reduce chamber volume if need be. At where your compression is a 64cc chamber is a maximum IMHO.

$.02 whether that much was needed or not..

[Mike C]

I also agree with the 60cc or less on the heads because of the pistons and how far down the bore they are. The dart S/R can be had in 58cc for less than $1000 and is a good truck head.

But if you really want aluminum heads, the Brodix IK, the Summit head (TFS made I’m sure since Summit owns TFS) or the AFR Enforcer head are all great. All can be had in 64cc I believe. I would choose a 180cc intake port regardless for your motor.

The EPS is an awesome intake, but square bore only. The standard performer should be more than adequate and let your Q-jet bolt right up.

I also would go with the Turbo 700 rather than the 350.

If running rams horns, of which I am a fan, I would only run the straight dump 2 1/2” corvette manifolds.

[dz1087]

Using Summit’s static compression calculator, it looks like I would be getting about 10:1 compression, assuming 4.020 bore, 3.48 stroke, 7cc dished piston, .025 deck clearance, .024 compressed gasket thickness, and 64cc head volume. With 58cc heads, I’m at 10.67:1. Would the 10:1 CR be too low for that Voodoo cam?

Should I look at running a size smaller cam? Or should I re-gear to 3.73 along with the 700R4? I’m not entirely against going with a head with a smaller than 64cc, but I want to run it on pump gas and do still want to drive the truck around town, not just hole shots at the drag strip. Just want some umph. I daily’d a 450 hp manual Mustang for about 5 years, so I like to scoot. However, it was the modern Coyote engine, so it had variable timing. I understand working with these older setups call for more compromises but I’m looking forward to learning.

[Tom]

I think you should go with the next step down in the voodoo cam line.

[garyd1961]

I know you said you wanted to keep the ram horns but a good set of long tube headers would really help those heads breath. Don't believe everything you hear about header leaks, a good set with good gaskets and re-torqued after first run will last 5 years I know. That's how many I have on mine with no leaks.
Oh yeah as Tom said don't over do it with the cam. With good heads, intake, headers, you don't need a big cam to make power. A smooth idling cam with stock converter will be a lot more driver friendly and still get up and go.

[dz1087]

Originally Posted by Tom

I think you should go with the next step down in the voodoo cam line.

AND also go with the 2400 stall/700R4? Or would the next size down be good with keeping the current TH350/3.42 rear?

[68post]

"7cc" is usually just the amount the valve reliefs contribute to a true "flat top" piston, you'll never achieve 10-1 with a dished piston and 64cc heads with only 355 ci..( in other words..if you have a dish and valve reliefs..then you have way more than 7cc to account for).
Please do not consider thicker head gaskets to lower compression, there's very little leeway when adjusting gasket thickness if you are staying within proper quench distance.

If I remember correctly a 383 only achieves about 10.7-1 comp with a flat top piston and 64cc. (5cc to 7cc for valve reliefs, and proper quench)

A '96+up vortec has a slight dish and is only 9.3 rated @ stock 350ci with it's claimed 64cc heads (not sure if it would measure out to a true 9.3 !!)

[dz1087]

Originally Posted by 68post

"7cc" is usually just the amount the valve reliefs contribute to a true "flat top" piston, you'll never achieve 10-1 with a dished piston and 64cc heads with only 355 ci..( in other words..if you have a dish and valve reliefs..then you have way more than 7cc to account for).
Please do not consider thicker head gaskets to lower compression, there's very little leeway when adjusting gasket thickness if you are staying within proper quench distance.

If I remember correctly a 383 only achieves about 10.7-1 comp with a flat top piston and 64cc. (5cc to 7cc for valve reliefs, and proper quench)

A '96+up vortec has a slight dish and is only 9.3 rated @ stock 350ci with it's claimed 64cc heads (not sure if it would measure out to a true 9.3 !!)

Good to know then, thanks.

I based the 7cc on looking up the stock dished piston cc amount and that was what came back. So you're saying to not go with a steel shim thin head gasket to increase compression?

[Tom]

Originally Posted by dz1087

AND also go with the 2400 stall/700R4? Or would the next size down be good with keeping the current TH350/3.42 rear?

I don't know. I hate automatics in general and bigger stall convertors on the street.

[68post]

Originally Posted by dz1087

Good to know then, thanks.

I based the 7cc on looking up the stock dished piston cc amount and that was what came back. So you're saying to not go with a steel shim thin head gasket to increase compression?

Not exactly.
Set your quench distance within the correct parameter of measurement.
You can adjust it tighter with a thinner gasket as long as you don't try to go too tight.
The extra compression gained is just a bonus and actually may help decrease knock tendencies and the extra compression is just a bonus, (it will only be a fraction of an increase after all).

IF the shim gasket sets your quench correctly and will seal your heads properly then by all means go for it, but those two must be met first AND without consideration of compression.
You set compression with the piston (dish, flat, or dome), and the combustion chamber volume - not head gaskets.

You should only adjust compression within the proper quench distance and is what most consider CORRECT, and a small block chevy can use it (quench, not all engines designs can do this).

[dz1087]

68post, Have you got anything I can read up on quench? My understanding of it sounds a bit different from what you are talking about here. I was under the impression that quench distance could be adjusted based on the thickness of the gasket used. This adjustment could be used to adjust the compression of the engine. The way you are talking about it here makes me think there's something more to it that I am missing.

[68post]

Please just do a search titled ; "Ideal quench distance" and you will find plenty to read.

[68post]

https://www.enginelabs.com/news/what...in-for-quench/

Here's the link you asked for.

[dz1087]

Back on this subject now:

Looking at a photo of my pistons, they are flat top, 7cc valve relief pistons. And they are some unknown distance in the hole. I'm assuming .020-.025 as I did not ask the machinist to deck the block, just square it up.

I'll definitely check the piston clearance when I pull the heads, but now I'm curious about compression. If I go with a 64cc head and a .015 gasket, I'm calculating 10.27 : 1 compression.

Is 10.27 streetable? Seems a little high. Any benefit with going aluminum to handle the increased compression on a street truck?

[kwmech]

Originally Posted by dz1087

Back on this subject now:


Is 10.27 streetable? Seems a little high. Any benefit with going aluminum to handle the increased compression on a street truck?

It is high to be running on todays pump gas. Aluminum heads will help with pre-detonation. OR if you plan on changing the heads go with a 70 ish cc head to bring the compression down. You didn't mention which camshaft you are running. I personally do not build anything now-a days over 9-1

[dz1087]

Originally Posted by kwmech

It is high to be running on todays pump gas. Aluminum heads will help with pre-detonation. OR if you plan on changing the heads go with a 70 ish cc head to bring the compression down. You didn't mention which camshaft you are running. I personally do not build anything now-a days over 9-1

Haven't chosen a camshaft yet. Any recommendations?

[geezer#99]

No expert here but when I last used aluminum heads I was told that a .015 shim gasket can’t be used. You need a composite (multi layer) gasket.
I wouldn’t decide on heads or cam until you’ve torn it down to see exactly how far the pistons are down in the hole.

[kwmech]

Originally Posted by dz1087

Haven't chosen a camshaft yet. Any recommendations?

Kinda depends on where your compression ends up with the chosen cylinder heads and what you want the engine to do

[dz1087]

Originally Posted by kwmech

Kinda depends on where your compression ends up with the chosen cylinder heads and what you want the engine to do

Fair enough. I'll sit on this a while until I get to the tear down portion and then start sniffing around for some recommendations.

[dz1087]

Originally Posted by geezer#99

No expert here but when I last used aluminum heads I was told that a .015 shim gasket can’t be used. You need a composite (multi layer) gasket.
I wouldn’t decide on heads or cam until you’ve torn it down to see exactly how far the pistons are down in the hole.

I've heard that as well, but then I've also heard guys running them with no issues.